I've had a dull ache in my testicle that comes and goes for the last 4 weeks, anything to worry about? I am a healthy 48 year old male.

Need more info... The reported info is not enough to tell what may have caused all your symptoms. To figure it our can be done by following instructions described in https://ebettercare.com/feel-become-sick/. Then you can work well with doc so to reach right diagnosis for right care, though clinically one needs to consider inflammation/infection, hernia, disorders of local muscles, joints, and nerves. All the best.