Hello and thanks for the query
There might be a soft tissue
or ligament injury
of the thumb tissues. You need to give your thumb a proper care and rest. Some of the measures that help you in getting relief are:
1. Keep the hand elevated as much as you can
2. Do alternate Ice and hot fermentation.
3. Take some analgesic
and anti-inflammatory drugs to reduce pain and swelling.
4. Restrict the movements of the thumb and wear a thumb support if you can.
Consult your doctor if swelling become worse or does not subside in 1-2 days.
Hope this will help you.