Thank you for writing to us.
Generally, blood clots do not occur without pain. I can assume that you have a single side swelling and with the history of travel, maybe to a mosquito infested place, you could have gotten filariasis.
Do not attempt to massage the area because if it is a clot, it can dislodge and block blood supply. The other causes of single leg swelling can be due to injury or tight shoes or the loss of pressure while flying.
I recommend that you see a Doctor to find the reason as soon as possible.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.