I highly doubt it's an abscess that is producing enough puss to be able to draw it up in a syringe without it being painful. A few weeks ago, I pinned a location that I had never pinned before, and the same thing happened to me. Im pretttty sure It's blood mixing with the oil, but if you want to be sure, u can get a blood test to check for infection. No MD I know will cut into skin looking for an abscess with no signs or symptoms of abscess. If you are just that curious, take an empty syringe, push all the air out, and stick the exact same spot you got the "yellow". Then aspirate. If you get whitish yellow fluid, then I would suggest going to an Md where they can do CT scans and such.