Feeling Overworked and Overwhelmed, should I leave or ride it out?

I’ve been at my company for 8.5yrs, have gradually moved roles and love the work I do today even though it can be high stress at times. I recently learned a new hire at a lower level than me (I’m in a Sr position) is making just shy of 4k less than me so of course I was pretty shocked. I did some research and found out that the average salary for my role (as a new hire) is roughly 20k more than what I’m at now. I already take on way more responsibilities and tasks than my role requires so I asked for a raise to match my responsibilities and I was told no. I’m completely overwhelmed and in shock and just feel like saying screw it and quitting. I’ve had time to process it and have slowly stopped volunteering to take on more work since clearly it’s not valued. I’ve gone through so much during my tenure and in some sense feel loyal to the company but after this, I’m not sure what to make of it.

Things change, and I know the situation will eventually get better. I’ve already applied for other positions internally and awaiting outcome. But would you stay and see what comes of it or just find another job elsewhere?