Not using Right Hand. Due to asphyxia.

Hi Sir / Madam, My son who is under going physiotherapy due to Birth Asphyxia (our pediatrician suggested to avoid complications in furure). By god grace and Doctors treatment he recovered and completed 5 months, From last 3 days he is not using his right arm (other than opening his fingers) at all, previously he w as able to lift both of his hands and we consulted Pediatric Orthopaedic (Physiotherapist expressed a doubt about muscle cramp due to the regular message which we are performing at home) and he said nothing to worry as there is no pain or swelling when he applied some pressure. But still we are having sleepless nights and waiting fr the moment when he use his right hand. Could someone tell us is this is normal or abnormal due to Asphyxia. Regards, Sai.N