Kingston is rather more serious - you've just cut off the primary rail lines between Toronto and Montreal and there are likely no ways around it (as both CN and CP's bypasses by then had had the rails removed) and Highway 401 is now definitely out of commission for at least a few weeks. It passes far enough away from RMC (presumably the target here) that it will more than anything be a matter of clearing the debris out of the way. Queens University is now history, which is a major loss for Canadian education, and you've probably just resulted in ~15K-20K civilian deaths and a lot of injuries, which will surely swamp hospitals in Ottawa, Montreal, Toronto and everywhere in between.
With regards to Kingston, where I spent a very good year to at grad school in Queen's and where I visited on an overnight trip just this May, things would be worse. CFB Kingston is literally just across the narrow Cataraqui River from downtown Kingston.
Using Nukemap assuming a 100 kiloton airburst explosion, the whole area of the base would be doused in lethal radiation, while the downtown will be levelled. There is a small possibility, I suppose, that its solid limestone will hold up, but I think it small. The area of Queen's, meanwhile, would be set ablaze.
With Kingston devastated, that whole part of eastern Ontario will be without its natural centre. A small mercy, I suppose, that Kingston is a relatively small city, home to a hundred thousand people at the time, but a small mercy.