Thanks for posting your query with us.
The pain you have looks like it did definitely start with the episode of pushing the motorcycle up on a stand. If the pain is radiating into one of your leg then you need to visit an orthopedic doctor. He would assess your pain and give you pain killers and medicines to relieve swelling. After the rest and medicines, you would need to start on physical therapy
to prevent another episode of a similar pain. The physical therapist will assess and teach you exercises for the strengthening of your back and once you continue the exercises for about 3 months you'll have a strong back.
If your pain at the moment is just in the lower back region and that to maximum on sitting then you can simply apply some heat and take muscle relaxants for 3-5 days and start with a few exercises. That should help relieve your pain. The exercises include
2. Knee to Chest
3. Straight leg raise to 30 degrees on both legs
4. Static abdominals
5. Hip abduction and extension
6. Cat and camel
7. Superman exercise for back
Hope this helps.
Get well soon.