I personally would not take a chance.

From Google: Step 1
Check the sell-by date on the container of whipping cream. Whether opened or unopened, as long as it has been refrigerated continuously, whipping cream should be good for three or four days past the sell-by date by conservative estimates -- some sources say up to one week. However, if you've already whipped the cream, it only lasts about a day in the refrigerator.

Step 2
Use your senses to inspect the cream. If you see signs of curdling or lumps, or if you smell a sour odor, the whipping cream has gone bad. Homemade whipped cream made from liquid whipping cream will begin to deflate and re-liquify, separate or turn yellow when it expires, in addition to curdling or developing a sour odor.

Step 3
Keep your whipping cream refrigerated continuously to prolong its life, and consider freezing it in an airtight container if you won't need it soon. To successfully whip frozen and thawed whipping cream, shake the container thoroughly to re-emulsify the butter fat. To freeze homemade whipped cream, spoon it onto a baking sheet in individual mounds, freeze and then transfer to an airtight container.

Souring cream makes great scones.

Trying to sour cream that has been processed by a dairy may not be a good idea. An inhibitor is often added by processors to milk products to lengthen its 'fresh' time. This inhibitor works against the natural bacteria based souring agent, and when the milk product begins to go 'bad', it may be based on a fungal agent rather than the natural bacterial one. The resultant product can be a disaster.

Good sour cream or sour milk is made from cream/milk that has no inhibitors. 'Starters' are often used. This is a bit of material from a former batch that had desirable features.

Personally, I'd toss any commercial milk product that has begun to spoil (unless I knew more about certain details).

I only use "soured" raw milk or cream. Never processed milk or cream.
I have several "sour" cream recipes from my grandmother. My mom was raised on a dairy farm.

Throw it away and buy a new carton. Why risk your health for a dollar or two????