Piston pin should push in with your thumb, applying moderate pressure. I had one once where I had to beat it in with a hammer and 3/8" socket extension and never felt comfortable with it. After about a year with no real problems I put in a new piston kit where the pin fit properly (of course I had to beat the old one out, too).
Did this pin come with the piston?? In my case, I was using a brand new, old Wiseco piston from about 1980 that did not come with the wrist pin and so I was using the old wrist pin from the previous piston, hence the fit problem. I fear shattered piston skirt could happen from too tight of wrist pin, but as I said, I never actually had that happen.