It's not clear what we are looking at or what the problem is.

There is no scale for example -- placing something recognizable like a dollar bill or can of Coke, beer etc in the picture can help.

Try to describe what you want to patch -- how deep, for example.

And say what sort of tiles. They can be really thin, or thick like horse stall mats.

You mentioned "first image". Did you intend to attach more?

Thank you for responding….Here is the same corner with a garbage bag in front. Please let me know if you need more detail for scale. The rubber tiles are 3x3, 8mm thick. My objective is to understand how to patch the area shown in the first image, between the cement wall and concrete flooring so that when the rubber tiles are in place, the wall completely intersects the tiles.

Arrows pointing to the location in the close up photo

Much better!

There are multiple products that would work and a web search for concrete wall patch will find products and videos.

One from Home Depot

https://www.homedepot.com/p/Quikrete-10-lb-Quick-Setting-Cement-Concrete-Mix-124011/100318542

That won't take much product and that 10lbs should be way more than you need.

Thank you so so much!!!!

I installed commercial rubber tiles in my basement which are likely to be somewhat stiffer than your gym floor tiles. My experience may not be exactly comparable but it is a similar product. 
We found that getting the surface suitably smooth to be more challenging than it appeared at first glance. My house is from the 1930s so the basement slab had many divots to fill. After that we had some ridges and valleys to smooth out. We could have chosen to rent the equipment to grind the slab but did not wish to go through that process. Instead we used an angle grinder to knock down the highest spots. Then we used a long straight edge to find the valleys for the first run with a portland cement based feather finish product. After that, we skimmed the entire surface and then used a rough stone to knock down any ridges before the product was completely cured. 
I don't know how picky you are and what final results are acceptable. For me, I expected to use the space extensively for many years so I invested considerable time and effort in surface prep. From a distance most slabs look flat but up close the low spots show up. Try mopping the floor and see where the water pools for a quick idea. If you expect to exercise without shoes or do lots of floor work, you will find your body can feel an eighth inch floor dip on a relatively hard surface. High spots aren't as obvious to me but a slight valley seems like a ditch to my stocking feet. If the surface isn't flat, the tiles won't line up evenly and since I had about 600 sq ft of 2x2 tiles, I wanted clean corners and tight seams.
We used a skim coat product from Uzin with the first sacks from ReStore. Additional product and the adhesive was purchased from the commercial flooring supplier where we purchased our wood flooring finish. They also sell the comparable products from Ardex. The product is not cheap but each sack covers a large area. Those products set extremely quickly so mix a small amount and be prepared to work fast. The Quikcrete product mentioned before is a good product for larger holes and edges but you may wish to use a finer finish product if you choose to smooth the surface of the slab before gluing the tiles.

This is how it's done with the right product.