Hi,
plantar fasciitis may be a reason for developing poor
postures and so hip pain. It is a variable but it is probable that there may have been others.
Analisys of posture, biomechanics and other plausible factors for developing hip pain (eg. leg length discrepancies) have a crucial role for your case. Spinal disorder may also be a reason of your symptoms.
The fact that your hip is not as flexible as the other and has limited ROM should be further ivestigated with an accurate physical examination. It is important to know when your hip aches the most, which movements and postures reduce your pain. Repeated movements may help better understand pain/ROM behaviour and in turn understand the suource of the problem. Can you upload your X-rays and US?
I would advise you to go to a physiotherapist to help you
Regards