my lens had a smudge mark on it, i don't know why, so i blew off the dust particles and wiped it with a eyeglass cloth. The smudge did not go away but just spread out on the lens. Is it safe to use a eyeglass cloth? is there anything else i can do without buying something from the store? i am very scared that i scratched the lens. I think the smudge could be a fingerprint mark so i am hoping it's not a scratch. What should i do? How does a scratch on a lens look like?