Suggest Remedy For Chronic Gastric Pain And Swollen Lymph Node

Hi. I recently been put on Nortriptylin (25mg) for severe chronic gastro pain due to a virus. I have only been on it for 4 days but I noticed that I developed a mouth sore on the inside of my cheek and in the inner part of my ear. I also developed a small swollen Lymph node behind my ear on my neck. Is this something to be concerned about? I read that it is possible for some of these side effects can hhappen, but how long till it becomes a concern or what are ways to prevent these or manage these side effects?