Yes, absolutely, you need to see a doctor. At a minimum you need a good physical exam (best done by a knee specialist) and an Xray.
The knee specialist can probably get the diagnosis by an exam and Xrays alone.
And yes, it does sound like you could easily have a ligament or meniscal disruption.
HERE IS A GOOD LINK ON KNEE INJURIES THAT WILL EXPLAIN THE DIFFERENT TYPES OF INJURIES POSSIBLE AND THEIR TREATMENT.
The chances that you need an operation are hard to estimate, but based on your symptoms I would think they would be fairly high, especially if you wish to return fully to sporting activities.
Based on your symptoms I would suspect a meniscal tear, a lateral collateral ligament tear, a quadriceps injury, or even a cruciate ligament tear.
The botXXXXX XXXXXne is that knee injuries are difficult to diagnose based on symptoms alone and you absolutely need specialty care as soon as you can get it.
Some money invested now is money wisely invested so that you may recover completely.
It is important to get this evaluation quickly.
You are in a time window now where an operation, if needed, could be performed as the initial swelling from the injury has likely resolved, and the sooner an operative problem is corrected the better the prognosis for full recovery.
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