Hello and welcome to HCM
A painful swelling on underside of the heel can be a 'corn'.
A corn is formed due to proliferation of upper layers of the skin. It is a harmless lesion and treatment consists of removal of the corn.
This swelling can be due to bony growth or any other
soft tissue growth.
X-ray of the foot will determine whether the swelling is arising from the bone or soft tissue.
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Exact diagnosis can only be made by clinical examination and investigations.
Consult your doctor for further management.
Thanks and take care
Dr Shailja P Wahal