My advice would be that you suggest for your boyfriend to go see his primary care doctor
about this issue. Most of the time, the types of knots or lumps that you are describing are not a serious problem; however, when they persist or enlarge, they should be checked out just to make totally certain.
One possible cause would be a persistently swollen lymph node. Lymph nodes tend to swell up after common infections like the cold, as they are involved in fighting off infections Although they are supposed to go back to normal size after the infection resolves, they do sometimes stay permanently enlarged. This is not usually a problem, however, rarely, a swollen lymph node can represent a more serious problem, such as a tumor, especially if it continues to increase in size.
The other possible cause would be a cyst under the skin. These are almost always benign and do not require further medical treatment. However, sometimes they can become large and be either uncomfortable or cosmetically a problem, at which point they may need to be surgically removed.
Your boyfriend can start setting up a routine visit with his primary care doctor when he next has some free time.