OK, the obvious questions......
Do you have mites? Mite bites can get infected and they do tend to congregate on the head area. Obvious short term solution is get rid of the mites.
Do you feed live prey? The prey while almost always losing the battle can get a bite or two in and inflict damage. If it is a rodent bite will most likely heal on it's own.
Is your snake eating and otherwise looking healthy? No signs of RI or listlessness? Any sign of other illness indicates immediate vet visit!!
If no other bad signs...
Switch substrate to paper type products until you know what's going on.
Closely inspect the area, looking for any inflamation, pus or anything else that would make you believe it's infected, if infected, see a vet!!!
Does it look like a scab? If so may be a healing wound - bite, rub or???
A pic from the side would be helpful
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
26.49 BRB
20.21 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

