I shaved my vagina & after that i got something like an ingrown hair(pimple) but now after 2weeks its now an blister. what should i do?

Consider: First placing warm compresses 10-15 minutes 3X/day over the next several days(to see if this will allow for spontaneous drainage). You also may place some over-the-counter topical antibiotic over the lesion too. But if it isn't getting better in the next several days or you have spreading redness and/or progressive pain or fevers, seek an inperson evaluation. You may need this incised.

Blister is no pimple: A pimple from an ingrown hair is not the same as a blister which can connote another condition like herpes. You need a MD evaluation to see what it actually happens to be.