That's a pretty crazy high HR for not running hard. Maybe this is something that you should talk to a doctor about. You can never be too careful when it comes to your health! Like anything else, though, I'm sure it will get easier as you go.

If I can´t run...I would die...
Not seriously...
I now my friend that this particular high HR is distressing and discouraging, remember that you were healing an injury...and no matter what you were, pretty much inactive for a period of time.
You need to take one step at the time, easy, and day by day.
I would like to know what is your current resting heart rate...I mean at the time you wake up in the morning?
Try to get also your aerobic base back with the other two disciplines. As UFTriGator mentioned, talk to your primary care doc just to make sure and rule out other things...to review if you are taking any medications, and so on...
Don´t panic, might be rough but you are a young guy and you´ll be back to normal in no time.

I'd say its ok. Work on your base using the other 2 disciplines and just start out slow, short, and regularly but infrequently and you will find that in a few weeks you'll be able to run at a lower HR. Try say 20 min slow every 3 days at first or something like that. Since you haven't been running and aren't in good shape, don't glue yourself to the HRM at first. Just go by perceived effort on running for a few weeks while your body adjusts to training again... I'd say its normal to have a higher HR after time off. Be patient, don't panic.

Your working HR zones do and will change with your fitness, and should be reevaluated with significant changes, say from inactive to suddenly trying to be active again. Not running for 4 months can make your resting HR and thus mx HR a lot higher, especially if you were fairly low to begin with (a lot of endurance athletes are). If you feel like your heart is going to jump out of your chest, see your doctor but start off easy. If it just looks higher than it feels, you may just need patience while you build back your base running fitness. 30 minutes at 170 will start to feel easier over time and eventually probably become 30 minutes at 140.

I was going to suggest the run/walk thing. It's highly recommended when getting back into running from what i've researched. But also, as others have said, for the first few weeks, ignore the heart rate monitor. Just go on how you're feeling. As you get your run fitness back it will feel easier to run the same pace, and when you check your heart rate it most likely will have come down from where you started.

That's it... I'm going to run without the HRM now and I'll be incorporating the run/walk thing till I'm comfortable enough to run the whole thing!

Thank you for your tips, folks!