If the muscles are getting tight after working out and you have loss of ROM (Range of Motion), some more stretching and self-massage will help.

If it's just muscle soreness after workout without loss of ROM, then just some self-massage is fine.

If you're NOT losing range of motion but they're just feeling "tight" all the time (as opposed to just the day after workouts), you need to build up strength and mobility. Make sure you are constantly stretching AND doing the strengthening exercises.

This article may also be helpful:
​https://www.uprighthealth.com/blog/how-to-relax-tight-muscles-fix-stiffness