Hi and welcome to HCM
Pea size ball on my upper left adbomen could be due to muscle spasm or tight muscle.Doing hot fomatation and applying muscle relaxant
gel will be helpful. You can take anti-inflammatory drug like motrin
to reduce pain and inflammation.
If you don't find any relief with the above measures, a detailed clinical examination along with appropriate investigations are needed to establish a diagnosis.
I do hope that you have found something helpful and informative and I will be glad to answer any further query.