Is the cut hot to the touch or anything like that? If it's having some trouble healing up, it's always worth going to the doctor for a look.
Make sure you wash the area with soap, you can also get some first aid antibiotic ointment and place the ointment on the cut- put a bandage over it to keep the ointment on, and try not to itch it or touch it.
Definitely get to the doctor if that doesn't seem to help.