You will need to drive to take him to a good vet with the knowledge and experience to treat rats (At times I have taken 2 to 3 day trips to a get to a good vet so I understand the effort it may take)
He needs pain meds - Metacam has anti-inflammatory properties
http://ratguide.com/meds/nsaids/meloxicam.php http://ratguide.com/meds/nsaids/ibuprofen.php
A vet may determine that he needs a steroid such as prednisone or dex (can not be given with Metacam and not with ibuprofen and there is a couple of days waiting period between the two meds).
He may recover from the injury with treatment, or he may not.
The main thing is to reduce inflammation, reduce pain, and provide a supportive environment
http://ratguide.com/health/basics/signs_of_pain_in_rats.php
Some elderly rats gradually lose the functioning of their hind legs and still have good quality lives in a modified environment
- provide soft padded bedding such as a cotton or fleece baby blanket (nothing toes can get caught in) - changed several times a day
- make sure he has easy access to water - water bottle, water dish that can not be upset
- make sure he has easy access to food - in addition to his rat blocks, you can soak the blocks in cool water to make mush, organic soy infant formula thickened with baby cereal is also good as it provides many nutrients
- soft foods are easier to eat. Other soft foods you can add include baby food, cooked vegs, cooked oatmeal, a small amount of greens, etc
- I would limit handling so his spine is not further injured ……. but if he does not recover, later he may need you to help him groom himself ) people use unscented alcohol free baby wipes, a warm damp cloth, or supporting the rat's body as the rat lies on their hand/arm and soaking the rat in warm shallow water in the sink. A clean new soft tooth brush can be use to brush him in those areas hard to reach without the use of back legs
Please see the Reference Thread for good information
https://www.ratshackforum.com/threads/reference-thread-read-only.35894/
and this link re care of paralyzed rats
https://www.joinrats.com/RatHealth/HindEndWeakness/i-TBWwhTt
I hope your little boy is soon feeling much better