Here you have told symptoms like pain at arm and hand level along with lump between your arm and wrist at inner side. I suggest to check do you have neck pain complain too. If yes then it can be related with neck pain. If there is no neck pain and pain starts only from shoulder level then it can be due to shoulder arthritis too. And if your pain is kind of radiating pain then it can be due to hypersensitivity of your upper arm nerves which is disturbed at either shoulder level or neck level or arm level. I suggest you should visit a orthopedic for proper examination and evaluation. Here he also need to see the size and location of the lump which you are talking about. Based on the diagnosis doctor will suggest for surgical opinion for cervical, shoulder or for lump area if there is any thing major. If there is no major problem in your x ray and examination then he will ask you to go for physiotherapy treatment and take few medication as a primary care treatment program and will review after some days. You can also use hot and cold pack at home for some more relief. Here since physical examination is not done by me I have given simple guideline on what to do. I suggest do not wait further because it will worsen your issue and then it will take time to improve. So just follow the suggestion and go ahead for treatment. And I am sure you will be fine with this. Take care.