Side-effects of steroid injections are very unlikely but occasionally people notice a flare-up of pain in the injected area within the first 24 hours after the injection. This usually settles on its own within a couple of days but taking simple painkillers like paracetamol will help. Each dose is released https://lhcathome.cern.ch/lhcathome/show_user.php?userid=2133890