Smashed thumb in trunk almost 2 weeks ago and severely cut it the cut it healing but still can't bend it and my hand hurts badly?

Tricky: without an exam, I can only give general information. There are a lot of possible reasons like an internal fracture, snapped tendons, bruises, etc. A reason for follow up fairly soon.

See a bone doctor: you need to see a hand surgeon to see if there is something they can do you might had a crushing fracture to your thumb, the skin on the top might heal but it take 4-6 weeks for the bone to heal. see a hand surgeon ,might be able to help you