It is recommended to pretreat clients who have a history of fever blisters with an antiviral medication by mouth to hopefully prevent fever blisters from occurring. I recommend treating 2 days before, the day of, and 2 days after injection. As to your question of popping blisters, it is not recommended to irritate or "pop" blisters. If this occurs, in all likelihood, the product which was injected will not extruded unless it was injected very superficially. I highly recommend you pretreat in the future with antiviral medication. As for the present if you have fever blisters, I would recommend you contact the provider who injected you and make that person aware. Antiviral medication such as Acyclovir or Valtrex may be prescribed at this time also.