Ptosis? Eye dermatitis? Why is the inner corner of my eyelid drooping? (Photo)

I tried to attach the best images that can show this but basically for months now I have noticed one eye is very off from the inner corner. It looks like the skin droops down in just one patch. It's puffy, and dry, and makes my whole eye itself feel dry. This is aesthetically affecting me because applying makeup is very hard now. I take care very well of my skin, and I am young (21) I would like to add that the rest of the eyelid feels normal!