As a DVT and PVT sufferer, get to the doctors or hospital asap! I had my first DVT a few years back and like you I assumed that I had pulled a muscle. I rode to work that day and suffered on the way home, once home I added a comment on Strava about what it felt like. A friend of mine suggested that it "might" be a DVT and to get it checked. Being a typical stupid old man, I ignored that advise and carried on riding!
Until it got to the point that I had to go see the GP, they gave me a blood test which showed that yes it was a blood clot the GP wanted to call an ambulance to take me to hospital!
However, not being one for fuss and also not really understanding the urgency of the situation I declined and decided to drive myself. But I called in at work first! At hospital the ultrasound confirmed what the blood test had already indicated.
I was immediately put on anticoagulants, in my case Rivaroxaban, while they carried out more blood tests plus many CT and MRI scans etc
Six months later after so many tests, no conclusion was made as to why I had suffered from this DVT. So the Rivaroxaban was stopped but I was told if I get another DVT, it would mean blood thinners for life
Guess what happened next....yep another DVT in the same leg a few months later, so back on Rivaroxaban. Meanwhile, more tests and then they discovered a PVT (Portal Vein Thrombosis) which has no real systems like a DVT, so it was a sort of blessing really.
So it was now back on Rivaroxaban for life and while on this a small lump appeared in the same place as previous DVT's, but no pain? More ultrasound and blood tests, but it couldn't be decided if it was yet another DVT or the remains of an old DVT that had not cleared?
Which meant I was forced sort of forced into upping my game and going on to Warfarin and consequently regular INR tests, which despite being one of the original and oldest blood thinning medications, it is still considered to be the best.
Plus, unlike the newer blood thinning medications, it can be reversed using specific medical treatments, the same cannot be done for the newer versions.