What should i do after being cut by metal door stopper?

Clean wound: Wash out your wound w/lots of water. Make sure you're not still bleeding. Make sure everything still works, eg you can still touch & feel as well as bend joints & pick up things. Assuming that it's a shallow cut w/o exposing tendons, nerves, bone, heck, even muscle, you might be ok at home. Still, you'll need to check for your last tetanus shot. Anything over 5yrs should be updated.