Yes can take paracetamol for headache but not frequently.
Because after CABG already kidney function gets affected and frequent pain killers may affect it more.
So take once in a while.
After CABG, post operative homeopathic tonics are helpful.
Start deep breathing and meditation.
DHMS (Diploma in Homeopathic Medicine and Surgery)
Homeopath, Kolkata
Good morning. U take a beautiful medicine. Gels - 30 / 3-4 drops with 2 teaspoonful water half an hour gap 8-10 times. From next day thrice daily in empty stomach. Azadirecta Ind. - Q / 30 ml. 10 drops with warm water half an hour gap for one day. Then 4 times daily.
Food normal.
Upto 1000 mg its usually not harmful until and unless you have other condition. The usual dose for adult of average weight is 650 mg that can be taken upto 2-3 times a day. So I do not think you should do anything out of fear. Just next stay cautious while using any medicine without prescription.