There could be several different explanations for this bump that you've just found. It is a little hard to tell from your question where, exactly, the bump is, so it is hard for me to narrow the list of possibilities down for you very much. I would recommend going to see your primary care doctor
, so that they can take a look and help you figure this out.
One possibility is that this is a lymph node (sometimes called "glands"). There are numerous lymph nodes in the neck and under the jaw which function primary to help fight off infections in the throat. If you are getting a throat infection or even a common viral infection like the common cold, these lymph nodes will frequently become enlarged.
This could also be a cyst under the skin, which is a benign growth which can develop pretty much anywhere on the body. The fact that it is not red and does not hurt make the likelihood of it being infected much lower.
Finally, there are some remnant structures left over from fetal development, such as thyroglossal duct remnants, which can sometimes be found in the neck.
Get in to see your doctor about this as soon as you can!