****UPDATE*****
Ok, so thanks for everyone's advice! I did what you all said and took Lola to the vet today. They tested the lump and didn't get back any results

but the vet said that is not necessarily a bad thing. He said that the good part is that it is not cancer or anything but the bad thing is they don't know what it is. My options were to either remove the lump and they would send it in for more tests, or just wait and see what the lump does. If it continues to grow or doesn't go away soon, I need to take her back. Hopefully it's just a bite or something and will go away soon. She seems to be doing great so I'm not too worried anymore.
However, I told him she limps a lot, and he confirmed that she has something wrong with her patellas (which I guess is pretty common in yorkies). He said she will probably have problems when she's older so they want me to think about surgery while she's young

!! I can't remember what he called it exactly but her knees pop in and out I guess. Poor little Lola...she was very scared at the vet but she's up and playing with my boyfriend right now! Thanks so much for all your advice!!! Greatly appreciated!!!