U just need to add a line to build.prop. search for it u may find it. It happened to my phone after I s-off my phone (its also wildfire s). And I suspect my proximity sensor is collapsed. May be the same case with you.
Open es file explorer
Go to system/build.prop
Add a line (gsm.proximity.enable=false)
Without bracket. Restart.
You should search about it and confirm first. I did this to my wildfire s. When u do it will be at your own risk and responsibility. It should disable the proximity sensor.
Sent from my HTC Wildfire S A510e using xda premium