Soo I have been learning Neon by John Mayer which has you fret the low E string with your thumb.. after doing it for a couple of days, I get this minor numbness on my thumb that sticks around for a few hours, moreso if I keep playing.

Is this something I should be worried about or should I just play through it? It's really annoying because I just want to play, and it doesn't really bother me, but I don't want it to lead to bigger problems down the line if it is something to be concerned about.

Any insight would be appreciated
If it only get numb when you play this particular piece... you're probably putting pressure on your thumb that is cutting off circulation. (That's purely speculation - I'm not a doctor)

Another cause of temporary numbness is lack of proper warm-up.

Get that blood flowing to your hands, and adjust your grip so it stays flowing.
You should never under any circumstance accept finger numbness as normal guitar playing.
I can't seem to help it.. my hands are particularly small. It seems any song that I need to fret with my thumb on that steel string guitar will do it.

I typically play a classical hybrid, but for this song steel string sounds much better, but is a little tougher on my fingers. So then I should be worried? I don't know what else I can do :\
Quote by Namzu
Med student here and I had the same problem a while ago. I went to see my doctor, and he said it's because i'm so skinny that a nerve got blocked. He prescribed me some Vit. B and it got better and it's almost gone. It can take a while (weeks-months) before it gets better tho.
If you feel anything in or near your wrist, go see a doctor immediately, as it might be carpal tunnel syndrome.
But don't hesitate to contact a doctor right now if you're worried, or if it gets worse.

Thanks for the tip. So did the doctor instruct you to take a break or were you still able to play while supplementing?