Hey there...
Its difficult to diagnose it here with the information that you have provided. It can be
1) Start of a Tennis elbow ( pain on outer side of elbow)
2) Inflammation of biceps tendon insertion (pain in the concavity of elbow joint)
3)Ligament sprain due to ligament laxity (in general elbow pain)
Next Steps
Try icing for a week and avoid the aggravating activity for 10 days ( especially KB swings)
If it persists beyond that go see a Physiotherapist.
The physio will examine the root cause and start the treatment with joint mobilisation and some pain relieving machines for faster recovery.
In case of tennis elbow ( all tight gripping movements will have to be avoided and use of a brace is recommended for 1 month post successful treatment)
Biceps tendinitis should go max by 10 days
Ligament pain might take 12 days to recover completely.
Remember... The pain shouldn't come back once it's gone.. That is the goal of the therapy
Health Tips
Follow physio advice during and post successful treatment