Is the sore wet or dry? It looks like it may be wet but I can't tell properly from the photo. If it is, cleaning GENTLY with very diluted hibiscrub on cotton balls, avoiding eyes, mouth etc can help to dry it out. Wash the solution off afterwards with clean water. If it is dry, unfortunately all you can do is wait for it to shed out- but make sure you help with shedding using humid hides etc if you don't normally, offered before the eyes go grey. Also you may need to apply hibiscrub soon after a shed as shedding can re-open the wound.
Other helpful stuff you can put on it- aloe vera (make sure it's the actual medicinal stuff, the 99% stuff from health food shops is good) and manuka honey have good antibacterial and healing properties
Hope this helps, had a really frustrating nose rub problem with a boa last year, kept looking crappy after sheds and hibiscrub really helped the healing process.