I have a Fender strat and the b srting on it makes a boing noise when i open strum it
I have noticed a dent in the string around the 12th fret. What should i do? can this be fixed?
start by replacing the string. probably replace all the strings.
and if you are new to replacing strings, do yourself a favor: remove and replace one at a time -- don't take them all off at once.
-=tension & release=-
There are a lot of things it could be... could you describe the sound a bit more... just saying a "boing noise" makes it a bit hard to diagnose. If changing your stings doesn't stop it, it could be many different things... fret buzz (you may need to get your guitar setup), or the fret work may be bad, the nut may be too low, the nut groves may have rough edges, or not be the right size for the string.. the list of possibilities is VERY LONG.
You might also want to clean out the B-string's nut slot if you only get the funny noise when you play the string open. That's a nice and easy, free potential fix.