Well from what you are describing there can be a couple of conditions which can cause this sort of pain. The first one which comes to mind is plantar fasiciitis which can cause the pain as well as the knot in the back of the heel. Now another possibility can be local tendonitis in which one of the tendons in the foot are inflammed leading to pain in the area, tenderness as well as pain which worsens on particular movement. If the pain is in the heel above the sole then achilles tendonitis can be a cause for this.
Now what you can do at home for this sort of pain is the following,
1) Use OTC motrin or aleve which can bring down the inflammation
2) Apply topical OTC voltaren gel which again will help with the situation
3) You can use orthotics which are available readily at your local pharmacy however these would help best once a diagnosis is made, as different orthotics are used for plantar fasiciitis and different ones for tendonitis
4) Physical therapy helps a lot in easing pain from fasicitis, you can contact your physical therapist for this
5) Night foot splints can also be very useful
But if you have tried all of these and they dont work, then you need a steroid injection directly into the inflammed area. This can be done by visiting your doctor. In most cases a MRI would also be done and after that, it would be easier to inject the steroids. But in the meantime try the OTC therapies which i have mentioned above, but you DO need to see your doctor. One thing which he can try is extracorporeal shockwave therapy which helps in some refractory cases where other therapies dont work.
Do you have any more questions?
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