My baby has fever blister on tongue n redness of gums n 2 pimple lik rash on face with v poor appetite?

Maybe herpetic virus. If you or someone close to the baby has herpes -- cold sores, etc. Then it is possible that your baby has gotten them. What you described is consistent with a primary (1st time) herpetic infection. Get to the pediatrician asap for diagnosis and any treatment.
Call pediatrician. Please call your pediatrician. They will know how to direct your baby's care. They will also know best your baby's particular situation. I hope you seek help soon, and take care..