Recent surgery l3-s1 currently have pain at si joints what can I do?

Osteopath. 48yo female post-lumbar fusion having "SIJ pain". Good portion of lumbar fusion patients develop SIJ pain due to upper body biomechanical forces focused on SIJ; as lumbar spring is disengaged. A SIJ belt might help; see Try gentle yoga and swimming. If pain becomes inveterate consider Prolotherapy via Osteopathy. Worst cases resolved by means of SIJ fusion. .