This is likely to be;
1) A muscle strain.
2) Myofascial triggger point. Trigger points may develop after an initial injury to muscle fibers. This injury may be a noticeable traumatic event or repetitive microtrauma to the muscles. The trigger point causes pain and stress in the muscle or muscle fiber. As the stress increases, the muscles become fatigued and more susceptible to activation of additional trigger points. When predisposing factors combine with a triggering stress event, activation of a trigger point occurs. Myofascial trigger point is a hyperirritable spot, usually within a taut band of skeletal muscle or in the muscle fascia which is painful on compression. The treatment is following;
1) passive stretching of the affected muscle after application of sprayed vapocoolant
2) physical therapy
3) deep electrotherapy; iontophoresis, phonophoresis, short wave diathermy, electrical stimulation
4) local analgesic patch / ointment / spray
5) anti-inflammatory analgesics; Ibuprofen (Motrin / Advil)
6) ischemic compression therapy; pressure on the points
8) steroid shots
You may get a soft tissue ultrasound just for caution. This will exactly diagnose the issue and rule out deep vein thrombosis (blood clot; though likelihood of this possibility is uncommon with your presentation.
Wish you a very happy, prosperous, healthy and safe new year 2017.
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