I ripped my hamstring in a tournament, on icy steps, over the week end. I've since healed it. No more pain anyway. If you've ever ripped a ham, it can last for years untreated. It's four days of treatment. I lost the match 7-6 6-4, but that was due to the rip. I'm not special. Before treatment, I had a ham rip that lasted 7 years. And I'm mid fifties, not 18.
You did not tear your hamstring, lose a close match, and then be recovered in 4 days. That is fundamentally impossible, and I mean impossible. You would be unable to walk if you actually tore your hamstring. Pulled muscles are ranked in "Grades", and a Grade 1 hamstring pull takes approximately 3 weeks from physical activity to recover. A Grade 3 is a tear and requires surgery and that many months to recover.