Hello and good evening.
Cracking of joints is very normal unless accompanied by pain or stiffness or other symptoms.
Regarding the pain in your thumb, it needs to be physically examined.
Next Steps
Physical consultation and examination by an orthopaedic surgeon. Can take pain killers occasionally.
May need Xray or local USG.
Health Tips
Rest the thumb if possible, avoid lifting anything heavy and putting load on the thumb. Ice packs or hot compresses both can be tried, use whichever gives better pain relief.
Take care and get well soon.