Lump under ear, cyst maybe?

Whilst I was combing Griffin thoroughly yesterday I found a lump under beneath the fur under his ear, it's not obvious as it has a bit of dry skin on it so has been there for a while but I comb his ears after every walk to prevent knots and haven't come across it previously. It's not tender or painful as he wasn't bothered by me poking and prodding it. I'm going to put some of the herbal cream I have on it and hope for the best but his boosters are due in a few weeks so thinking I will just mention it to the vet then? Don't want to make a big deal about it with the vet just a bit concerning as it's quite sizable and he's still so little!! Have googled and tea tree seems to be recommended which makes sense as it's an astringent but if anyone has any other suggestions I would appreciate them!!