Pry the flower and glue off. By gluing together the top of the plant, which is where the new growth comes from, the plant's ability to grow normally is severely restricted. You can see that in the picture- all the little bumps are being pulled together instead of spreading apart as the cactus grows.

I've had good luck gently and slowly prying up the edges of the glue so that it comes off without too much damage to the plant and spines. If you can't get a grip with your fingers because of the spines, try tweezers. Sometimes, though, the glue just won't come off the spines and I have to snip them with scissors. I try very much to avoid any damage to the plant body itself (the green part).

It looks like it's in a very peaty mix, so yes, repotting would be a good idea. A good starting place is to mix commercial cactus and succulent soil 50:50 with perlite to get better drainage. If you search on here for "soil mix" or "gritty mix" or "why is my cactus not doing well", there are a ton of threads discussing this.

The good news is you've kept it alive for four months! Great!

I hate those stupid flowers. I wish they would stop gluing them on.

Thank you everyone!

also... Do you have any suggestions on where to find those soils? I checked Home Depot and Lowes and no cigar !

Home Depots/Lowe's almost all have bags of "Cactus and Succulent Soil". However, these are still not ideal and it is generally best to buy a separate bag of perlite and mix the two together. This gives a little more drainage. If you really get into cacti (and they can be addictive!) there are good threads here on making your own soil mixes that are even better.

Be really patient with removing the glue. I tried a bit too vigorously on one of mine and broke off a piece of the cactus. Even with letting it callous and kept the top dry for months, the first serious rain storm caused it to rot. :(

Thanks a lot again!

i replanted my little one with perlite and the soil (bought them seperatly and mixed as recommended!)

Now one more thing! Watering... I read how you have to wait at least a week before watering a newly transplanted plant... How much should I give it? And where? I also read how you should water from the bottom, but some are saying water at the top until you see it coming out from the bottom

I water it about 1/2 cup water for that sized container. Let the soil dry out before watering again. Good choice with the perlite, I used perlite mixed with cactus soil. You should give it filtered sun, not straight sun.

Inside especially full sun. Water on top and let it run through. Use warm water and water in the morning ideally. Also these need more water and more often when actively growing but very little in the shorter colder days of winter when dormant.