White painless bumps inside my cheek. What doctor I should go see?

It could be a cyst or an abscess.
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.

Your local GP should be able to forward you on to a surgeon if the needs be but don't get worried, go to your doctor first

Actually it could also be a swollen lymph node and usually will clear out itself.
Hope I helped

your reg doc.