Foot Pain outside ball of foot

Hi there! Training for the nyc marathon and have had some pain on the outside of my left foot (underneath foot, just on the far left outside near the outer bunion).

This pain feels like a bruise and only is felt during impact. Not sure if I should rest or what is the best approach to improving this if there are any exercises I should be doing?

For now have been rolling feet out prior to run and trying to incorporate cross training but would love insight as to what this might be / exercises to help. Note this is not the arch of foot, it’s more towards the front of the foot on the outside.