Hello and welcome.
Thanks for your query.
If you don't mind me asking, did you witness this as well? Were you present when this happened and you saw the 'bump' like protrusion from his chest? Or was it only your boyfriend who noticed this?
If you did, then may be you should wait for it one more time and then try to either take a picture of it to show a doctor or rush him to the ER.
If you have not noticed this, then it is best you again wait for a while and see if your boyfriend experiences the same thing. Try to ask him to take a picture of it immediately, so that you and the medical experts can see it for themselves.
If your boyfriend fails to produce any proof of this I would be thinking about something else.
There is also a more likely condition he is suffering from called delusional parasitosis
Kindly try your best to monitor him at all times, and report any abnormal behavior to a doctor when you meet one.
I hope I have succeeded in answering your questions, you could write back to us anytime for further clarifications.