Absolutely p-static.  Very typical and normal when there is no exit from the paint to the wicks in the flight levels in dry precip.  That little explosion burns pin holes in the paint which is different than erosion.  The pin holes look like something popped in the paint or that a paint defect was present.  They are typically circular.   I don't know the scheme of your primer and materials but it is classic.  We even had it on the TBM using certified boots until they put some BFGoodrich antistatic glue bridging the rubber boot to the metal wing.   What's the paint system and the ground system for p-static?