It is not a risk as far as hiv is concerned
The HIV risk in your case is zot, zilch,etc..you can relax and take it easy.
The submandibular gland you are talking about are exactly that.....submandibular parotid glands... they are not lymph nodes (nodes are not glands). Submandibular lymph nodes are adjacent to the parotid glands. you can feel the glands all the time with a little agitation under the jaw. but your lymph nodes, when they swell, can be easily felt next to these elliptical balls that you are feling right now (parotid glands)
don't play with them too much or they will swell a lot and you will be convinced you have HIV.
God Bless