Hello there, I understand your concern about harming yourself with the accidental needle prick injury. Please do not panic as there is nothing to worry. The insulin in the syringe or the needle is not going to harm you in anyway. Without pushing the plunger insulin does not enter your skin and even if it does (a small drop that is present at the tip) its not going to cause any harm to you. People who are not diabetic anyway have a good feedback response and sugars will not fall with such a small dose (drop) of insulin if at all. Needle prick injuries can pass on viral infections like Hepatitis B or HIV and so one needs to change the needle if accidentally pricked someone other than the person intended for use. Considering you know your and your father s status of these infections I would suggest be careful every time you handle these needles. Moreover these insulin needles are very thin and can get bent if hits something accidentally and then will not deliver doses correctly. So be careful while capping the needle and using it. So nothing to panic in this case. Just discard that needle and use a new one if at all it ever happens again. Hope this answers your question. Take care.