Lele's great 
I had this problem with my panther. Fist, congrats on noticing it. It can lead to problems, and it's good to see you are looking after it instead of just waiting for it to go away! Hurrah for you!
Second, here's my advice:
1) rinse tail of debri. To do this just run it under tap water, warm but not hot. You may also need to wash with handsoap (just a bit). some oils leave buildup after repeated use, and this may be a problem.
2) rub a few drops between your fingers and massage cham's tail, using downward strokes. He/she will probably try and pull the tip away quickly. Hold on with enough force to rub a little, but not hard enough to hurt (a gently "tug" i guess)
3)Feed him/her a treat, and put back in cage.
I would try to do this after mealtimes, just because some chams won't eat after small stresses like that. If this isn't a prob then don't worry about it.
4)repeat morning and night, until skin looks all better
If this seems a little too "personal" (for lack of a better word) for your cham, use a q-tip and massage with gentle downward motions while holding the tail in your hand. You don't have to rinse every time, but every few days will help remove old oil and skin.
If things don't seem to clear up, or if they get worse, you may want to see a vet. They can give you a water based gel to use (that's what I used with Orion) that is to help guard off infection. There is lots in a tube, and may be useful later on. I find Orion's tail has problems every few sheds, regardless of misting, etc.
Hope that helps!
~Lindsay