Around 3days ago, i headbutted something by accident and my lip got caught on my brace, it turned into an ulcer and now the top of it has turned green?

Likely infection: Looks like your lip is getting infected. You should get it looked at by your physician.

Lip trauma: Get this traumatic wound checked by your orthodontist or dentist. If the swelling and pain are increasing there may be an infection that needs to be treated.

Be patient: The soft tissues of the lips swell easily turned into an ulcer when injured. The healing time for a lip injury will depend on how badly it is. Be patient for 7-14 days.

Should be OK: Keep your mouth immaculately clean. Call your Orthodontist schedule an exam jest to be sure your soft tissues are OK, and to have your hardware checked.

Traumatic Ulcer: You have a traumatic ulcer. The good news is that they usually heal in 10-14 days. The bad news is there is nothing you can really do to speed that up. The white/green color you see is the dead tissue at the border of the ulcer. It is normal and will go away as it heals. Rinse with warm salt water to keep it clean and avoid spicy and acidly foods as they will make it hurt.