I had calcaneal bursitis as a teen, so treatment may have moved on since then.
In your teens the bones of the heels haven't yet fused, and X-rays showed that the swelling was pulling them apart. So I was immediately put on crutches, not allowed to weight-bear on the affected foot at all, and given hefty doses of anti-inflammatories.
After two weeks, my other foot followed suite. I now had bilateral calcaneal bursitis, which triggered blood tests to see if there was an underlying auto-immune condition. Fortunately there wasn't, and treatment continued conservatively - rest and anti-inflammatories. Legs elevated whenever possible, cool packs, crawling around the house to keep mobile.
I was walking with crutches after a couple of weeks, and off crutches after another 3-4 weeks. It plagued me for several years, and as soon as I got any twinge I would start anti-inflammatories and cool packs. It never knocked me back completely again, and didn't stop me skiing. Though skiing sometimes triggered it.
It's not something to take lightly in a teen as it can cause permanent changes in the heel if left untreated. I would except physiotherapy to be part of the treatment nowadays.