If you see another bump, go see a dermatologist. Get it biopsied if possible to know what it is or isn't.
You were never tested for HPV. Men cannot be tested for HPV except via a biopsy of a wart. Only women can get tested for it,. No sexually active man can say they "clean of all stds" when they cannot be tested for HPV. It just doesn't make sense.
Since you admitted to having "a couple of one night stands", it could have lead to a HPV infection that you never knew you had. Especially if the sex was not safe. Since we all know that condoms provide little protection, safe sex doesn't really matter when it comes to acquiring HPV.
If your GF had a negative pap test (assuming this is not what she meant by clean of all stds), then she still could have infected you. Some women have it in such low levels that the tests they may not identify it. This is why women can go from being positive to negative within a year or two. The virus never leaves the body. But do ask her when her last pap test was to see if this is what she meant. If she didn't have a test before sleeping with you (and after sleeping with someone else), then she has no idea if she had it too or not.
All of this may not matter now. If you have it, so does she. She should get tested for it asap. If she gets a positive result, you have it too since you slept with her. You will never know who gave it to who. Neither of you can point to any past sex encounter and prove that the infection occured at that time. Men are usually the carrier since they cannot be tested. Clearly, the more unsafe sex either of you had was riskier but since condoms provide such little protection, all sexual encounters are risky. HPV (and also Herpes) is why the CDC says that only safe sex is no sex. :(
Your health and hers are the only important things now. Get her tested. Get your wart biopsied if your doctor agrees to it. Get past this like most people are doing.
also, i have been sleeping with the same girl now for 3 months. she claims that she was tested before we began dating and was clean of all studs. Had a couple on night stands before her. I was tested and was clean of all std's October 2013.