Yes applying some heat to the SI Joint Pain is good for it and helps ease the pain from the SI Joint pain.
When I have SI Joint pain I use a heating pad to help ease the pain of the SI Joint Pain and it does help.
If the SI joint pain is mild and not severe then the SI joint pain should go away and heal up on it's own within 2 days to 14 days.
More severe cases of SI joint pain may last for a month or longer and may need treatment by a doctor to manage the SI joint pain.
When my SI joint pain flares up the SI joint pain is just mild and goes away within 4 days of it starting.
You can take some pain medicine and apply a heating pad to the SI joint pain area to help ease the pain.
After a few weeks the SI joint pain should go away and if not or the SI joint pain gets worse then see a doctor about it.