hi. pharmacist.
the aspirin will be fine, and it isnt terribly liver toxic anyway. dont bother with the so called liver protectants.
there are some doctors who prescribe aspirin to patients but that is usually for the purpose of allowing the patient to claim a rebate from either government, or their insurance company. in australia for example pensioners only pay $3.60 for their drugs, and the government pays the rest, so you get doctors prescribing 300 aspirin tablets (essentially a years supply and 5 boxes worth) and the patient only pays $3.60 for the lot, rather than 3.60 for each box, which would be the case if they bought one at a time
i get the feeling that the doctor didnt "prescribe" aspirin, but rather suggested it. OR it was a combination pain killer with aspirin and codiene phosphate in it.
anyway, cut a long story short - just do exactly what your doctor said, your liver is safe.
cheers