。
My side hurts a little.
Literal
Side [subject-が] a-little painful.
A short pain complaint. 脇腹 (わきばら) 'flank, side of the body' — 脇 ('side, under arm') + 腹 ('belly'). Specific to the flank area where one's side is, below the ribs. ちょっと ('a little, a bit') softens the complaint. 痛い is the standard i-adjective for 'painful'.