wet head

hi, there is a wet patch on my cat's head.. the part between the ears... he was sleeping on my table and i just noticed it. i was petting him a few minutes earlier and it wasnt there then. he is an indoor cat and remains in my room for the most part of the day so i dont think he injured himself. plus the area under the fur looks fine, no bruise or anything. he is just 3 months old and short-haired..
can anyone help tell me what it is ? do i need to have a check with the vet ??

Do you have any dripping water around?  If you have a fountain for him to drink from, it's possible he got his head wet from that, or he might have tried to drink from a bathroom faucet (or played around it), or even just played with his water dish and splattered water on his head.  Anything like that is possible.  I would say if you don't see any wound on is head, and he doesn't act any differently, then I probably would not worry about it. 

@mrsgreenjeens

actually that is the weirdest thing, i do not have a fountain nor does he like to drink water to begin with actually. i have to mix water in his food to get him to drink. he was sleeping on my desk for about 15minutes and i was petting him and then suddenly i noticed the patch of water on his head. although like i said i checked the area there wasnt any bruise or injury in the skin but it smelled like his spit and cuz it just magically appeared there somehow so i got a bit worried..

lol im actually a new pet owner and i love animals to death so i tend to get paranoid if something out of ordinary happens.. but i monitored him today nothing of the sort happened again..