I've developed a pain in the underside/inside edge of the ball of my left foot, probably first noticed it early feb. It's hardly noticable most of the timebut has become increasingly painful when putting a lot of weight through the toes on less steep ground when climbing, and in the last week or to even when bending the big toe in trainers. No significant impact I can recall to set it off. I didn't climb for a week over half term and it hasn't improved. Thought it might be new trainers that are a little narrow, but haven't worn them for around a fortnight with no improvement either.
Any ideas what might be going on and how to treat it?
edit: corrected outside to inside