Can an abscessed tooth cause postauricular lymph node to enlarge? Node is smaller than a pea, does not hurt? Should this be checked immediately?

Not something urgent. This can wait until your infection improves. I like to give a couple (2-4) weeks at least if an lymph node is enlarged after an infection. If the node itself is getting large, the skin around it is red, and more painful, then, yes, this is something to see the doctor for right away.
Likely infectious. If the abscess is on the same side as the lymph node, it's likely related. However, if the infection in the tooth resolves and the lymph node doesn't then a thorough ENT examination is indicated. Lymph nodes in this area can arise from numerous processes in the head and neck.
Don't worry. It is likely to due to the abscess, however, if you have had this enlarged lymph node for at least 2 weeks then you should have your primary physician examine it. This lymph node may have been palpated on a prior physical examination and they can best determine the next step in management. If it is due to the abscess then spontaneous resolution would be expected.
It may. Postauricular lymph node maybe enlarged especially if it's a mandibular tooth in the posterior region of the mouth. If there is swelling associated with the tooth than this should be checked immediately.
Yes it can. Abscessed teeth produce a fluid of bacteria that drain into the lymph nodes of the head and neck region. The location depends on where the abscessed tooth is located. An enlarged lymph node can have many causes some of which can be unrelated to the structures that drain into it. It is best to have an oral surgeon or otolaryngologist check the growth.
Yes. Due to the manner infections spread through tissues and alert the immune system for a response, it is reasonable for lymph nodes to enlarge. It should be checked, and noted in the the patient file.