I dont think its anything serious it might just be your musels(sorry spelled wrong) sore from starting a new routine
You likely have bruised meniscus. These are the shock absorbers in the knee (two per knee, medial and lateral, medial inside, lateral outside). Good policy is to give every muscle and joint one day of rest for every day practicing/training. You can work out every day, but work different things. Wait 3 days and if it still hurts see a doctor. Skip your PCP if you can and go to an Ortho. Sounds to me like you'll be fine with rest...