Do I tell other job I got an offer while still interviewing?

I am a new-ish grad (8 months) working in social media within entertainment/media. I've been looking for a new role while working part time in my field (in a job I LOVE) and got an offer last week for

I am a new-ish grad (8 months) working in social media within entertainment/media. I've been looking for a new role while working part time in my field (in a job I LOVE) and got an offer last week for a job at an agency. Decent pay and exposure, but not in my field of choice and not super stoked about it. I signed the offer letter today because it felt dumb to turn down since it's stable and the only full time salaried offer I've gotten. BUT I'm still in process for 2 more jobs that are much more aligned with what I want to do. 1 of these jobs, which I would say is my top choice, I am waiting to see if I made it to the final round. I was talking to the HM last week and he said I would hear from him shortly as they had internal delays with July 4th. Our rapport has been great and the process has moved super fast, any time I have emailed him he has responded within the hour. I know nothing in this job market can be taken as a good sign and trying not to get my hopes up but I have been cautiously optimistic about maybe getting an offer. Was wondering if I should let him know that I got another offer with the hopes of speeding up the hiring process? Or if I should say I'm in closing stages with another interview process? Will he get turned off by the whole thing and pass me by/ghost or does it have a chance of being helpful? I've seen mixed things on here