About eight years ago I was training for a half marathon.  I recall having some discomfort in my groin area but thought it was just a tight muscle from overtraining as I was running 30+ miles/week.  The half marathon came and I loaded up on Advil and ran my best time ever but the last two miles really hurt.  When I got home I had to dig a pivot out of the mud and as I was carrying a bag of lava rock I slipped......and screamed in pain.  Dad asked if I was ok and I was definitely NOT ok.  Somehow we got the pivot out of the mud and I was able to rest in the house with ice.  I took it easy for a week, ran once, and it hurt but I could run.  The next weekend I ran another half marathon but was 25 minutes slower than the first one.  I shut down the running and a few weeks later went to the doctor.  Nothing conclusive.  I continued to take it easy and tried to jog a few times but didn't push it.  A handful of times I ran 100 yards and walked home and I'm not to proud to admit that I cried a few of those times and cried in bed a few times at the prospect of not running again.  Another doctor visit but this time with my preferred doctor who also had a history of athletic training and sports medicine.  He had me lay on by back on the exam table while he put pressure on my problematic leg and told me to sit up.  I could not do it without rolling to my right side.  He diagnosed me with a sports hernia, which is not the same as a inguinal hernia.  I had torn (or partially torn) my lower aductor muscle off my pubic bone.  Surgery is rarely recommend and generally done on professional athletes for a faster recovery.  I took about 6-7 months to recover and another 12-14 months to correct some of the issues I created by walking and running wrong for a long time.  Most of those issues were hip flexor and IT band related.

So to answer your question.....I do believe torn muscles can repair themselves IF they are not completely torn or separated from the bone.......and I'm not a doctor and did not sleep in a Holiday Inn last night.

I vividly recall watching Nick Bosa playing football for Ohio State.  He got hurt in a non-contact injury and curled up on the ground in a fetal position with his hand pressing on his groin.  I told my wife before he was off the field he had just torn a groin muscle and is college career was over......and I was right. 

Go see a doctor.