It sounds, from your description, like he has developed bursitis as a result of the injured bone. The swelling can put pressure on the nerves running around and through the elbow, which can cause numbness and tingling further down the arm.
Splinters, or chips of bone around the elbow is called "osteochondritis dissecans", and if you click on that it will take you to a link for more information about it.
The normal treatment for this is conservative at first---rest of the joint, application of ice periodically, anti-inflammatory medications, and some people are actually given a splint or sling to help rest the elbow.
It sounds like this type of treatment has not worked, unless he is not adequately resting the joint to allow healing. Sometimes the splinter(s) are too large to allow healing and have to be surgically removed.
It is possible to sustain this type of injury if the triceps muscle (back side of the upper arm) puts too much strain on the elbow where it attaches. He may have injured it during his jujitsu sessions and did not realize it at the time.
So, what he needs to do now, is see his doctor again to discuss the possible need to remove the chips or splinters that are probably causing the swelling (and so the pain and numbness). Keep in mind that conservative treatment will take some time for healing to take place. But if it has been 6 to 8 weeks without improvement (or it is worsening), he should definitely be talking to his doctor again.