Soft lump on lower jawbone?

Hello
I had a root canal about 3 weeks ago which went well. No pain now, everything fine. There was lot's of pain before I had it done though and I took anti inflammatories that helped it. I have lost about 2 stone last few months purely due to eating healthy. I noticed a soft lump on my lower jawbone( under the skin right hand side slightly lower than my ear) which feels like it is coming from under the jawbone and then it goes up my cheek about one inch, so tear shaped. It moves slightly when I touch it.Feels stringy. Never noticed it before. What could this be? Are there tendons in this part of the jaw? It does not hurt, although it has become slightly tender because I have been poking it. I am quite thin faced so maybe all I am feeling is a muscle or tendon? I do also get a mouth ulcer in same place on bottom of my tongue near tip when I get low or stressed about 3-4 times a year, have one now.

Any advice on this would be great.
Thanks