Have what looks like a blister with a white center where one tonsil used to be. Sore throat and nephew had strep about a week ago, could I have strep?

It's possible. Generally with "classic" strep throat the tonsils are red, have pus on them, but it sounds like you had your tonsils removed? You could still get a strep infection, just not strep tonsillitis. The only way to really know is to get a simple strep test - takes about 5 min to do. See your MD or go to an urgent care (NOT the ER!) There's no home remedy for strep, so if it's positive you need meds!
Yes. you could have Strep throat but the only way to tell is to be examined and have testing done. This is not an Emergency so you can wait to be seen until the morning. Use symptomatic therapy with tylenol, (acetaminophen) throat lozenges and lots of fluids in the mean time.