The cause of testicular pain
is ascending infection from the long standing indwelling catheter.
The most optimum treatment in your case would be the following.
1. Insertion of a suprapubic catheter which drains urine better and will reduce the infection spreading to the testis. ( the perurethral foley's catheter should be removed)
2. Regular bladder washes with saline till the effluent is clear.
3. Urinary antiseptic such as norflox
in dosage of 400mgm twice a day for 10 days.
I am sure this will help in preventing further damage to your urinary system