Black splotch or patch in left eye when I look up. It's mostly at the top of my eye, and my eye feels sore at the eyelid. Any ideas?

Get it checked! Dark patch in your upper vision is not normal, could be a retinal detachment. You need an eye exam within a day or two. The soreness is hard to connect to the visual symptoms. A sore eyelid in a 20 year old is usually nothing serious. It is often an inflamed oil gland and is help with hot packing. The exception would be significant pain and spreading redness which could be an infection.
Floater or FB. This could be a foreign body under your lid. You should have your eyes checked and your doctor could flip your eyelids to look under to see if something is making your eyelids sore and causing the black spot. It could also be a floater in the back part of the eye. Either way, it would be in your best interest to have an eye exam.