One slightly enlarged hole shouldnt make much difference on your machine...
Ensuring the grounds are evenly distributed and tamped is however very important.
If you have much (or any) clumping of the grinds, it is worth making an effort to break it up, I use a very small fork (the type you might pick up a pickled onion with) and circular motion around the basket.
Tapping the PF on the bench (up and down, not sideways) will help to settle the grinds more evenly before you tamp.
Good even tamping will help, depending on the clearance of the tamper in the basket, you might need to tamp in the centre, then move to North edge, retamp, then south edge, retamp, East edge and West edge, etc....doesnt have to be literally N,S,E & W just 90degree increments around the basket.