Monday my foot hit a door. big toenail came straight off. now i have swelling and pain on the big toe and the top of my foot. could i have broken it?

Surely: An x-ray would be needed to tell. Or you may have a contusion. You also want to make sure you do not get an infection from the nail ripping off and that the nail bed itself is not lacerated. A podiatrist would be able to check all these things. Ice your foot until you can see one.

Yes: But you may want to make sure you are not developing an infection. Clean the wound very well with water or peroxide otc antibiotic cream and bandage- then see your podiatrist for x-ray and evaluation for infection.