What should not happen now is, that the general public starts taking the drug as a precaution, just because it might work. The known side-effects are too severe (e.g. blindness) and also, there are already shortages of the drug for those who already require it as part of their medical treatment (e.g. immune-supressed).
This side effect occurs if you take chloroquine for extended periods of time. Look at the data.
https://eyewiki.aao.org/Hydroxychloroquine_toxicity
"Risk for toxicity is less with <5.0 mg/kg real weight/day for hydroxychloroquine and <2.3 mg/kg real weight/day for chloroquine[2]. Patients are at low risk during the first 5 years of treatment."
And management is as simple as stopping the drug if it starts affecting your vision:
"At the first signs of retinal toxicity, hydroxychloroquine should be stopped to prevent further retinal damage and visual loss[2]. "
Common (1-10%): rash, itching, diarrhea, vomiting, loss of appetite, headache, blurred vision, "Affect liability" (got no idea what that is).