Tendon and muscles. ... well it will get conformed by performing few test. Looking onto your details, it can be DOMS or muscular strain.
Next Steps
Don't neglect and go once to ortho or to physio for confirmation. online will suggest yu so many stuff on the basis of your sign and syptom.
Health Tips
Apply ice pack.(min 3-4 day)
Yu can spray volini or other pain relief spray
Don't bear more weight on affected leg.
Progress to minimal free movements.
then to walking.