Along with the anti-inflammatory try to keep him on soft bedding or in a sandy run with no opportunity to roost.
The formulary in the link below is helpful (actually, the entire book can be downloaded for free):
ACETYLSALICYLIC ACID - Aspirin (Butler; Vedco)
Available as tablets (5 or 60 grain) for oral administration. Also
available as 1.25 grain orange-flavored chewable tablets. May be
effective as an analgesic, antipyretic and anti-inflammatory agent
in some avian species. May be indicated to prevent clot formation
and embolisms secondary to egg-related peritonitis, granulomatous
diseases and shock. Uricosuric at low doses and may be
effective in some cases of acute and chronic gout. A five grain tablet
can be mixed in 30 ml of diluent and administered at a dose of 0.5
ml/kg, TID (or 1 tablet per pint of drinking water).
from: Avian medicine: Principles and Applications (formulary chap. 18) :
http://www.avianmedicine.net/ampa.html
(most OTC Aspirin is 81mg/325mg.).
Good luck!