The thing is I'm going to have a trip to Toronto in 1-2 weeks and I'm planning to have medical examination done while I'm still there (my city doesn't have any panel physicians listed on cic and honestly it's a pain to have multiple trips to the same city in the same month). I haven't received ITA yet, but I just received PT nomination so I should be qualified to received ITA next round (which I'm not sure when, next week, in 2 weeks or next month).
you can. CIC advise not to as the medical still needs to be valid when you land and no one can really predict when they'll get an ITA. However if you're confident you'll get an invite shortly there's no reason not to.