I have a pain in my right foot heel spur muscle --what could it be?

Heel pain. Depending on where the pain is exactly, it could be plantar fasciitis, achilles tendinitis or something else. See a podiatrist for definitive diagnosis.
Plantar fasciitis. It sounds as if you've developed plantar fasciitis, an inflammation of the main fascia of the sole of the foot. These respond to rest and stretching as well as ibuprofen. Resistant cases are handled by podiatrists.
It could be the spur. Which incidently is a piece of bone and not a muscle. Or it could be the broad banded ligament attached to the spur called the plantar fascia this is assuming you do indeed have a spur which is a radiographic diagnosis.