It looks like mold. It probably was introduced into the luan wood at the time of the leak. Now the residual moisture and life forms developed into those little bubbles.
You can very likely "get rid" of the bubbles by puncturing them with a sewing needle, 9at the bottom). I would then spray the area with the punctured holes with Lysol spray. Then, I would dry it out while ventilating the area thoroughly, (use fans).
Lastly, using some thick paper to protect the vinyl, I would use a flat iron and squash down the bubbles with the heat, (go from top to bottom with the warm iron).
BTW, In college I used to buy nasty old RVs, very quickly restore hem, and sell them to European vacationers "On Holiday". I ran across MUCH larger bubbles!
I never had any complaints, (actually received many referrals), as most vacationers would sell their trailer at a profit, (or sell it back to me for a nominal fee), before returning home.