Translation:Dikkatli ol ki yaralanma!
Is yaralanma here not the noun ("damage, injury"), but rather the negative imperative ("do not injure" etc.)?
Yes, it is the negative imperative.
Can we say: "Yaralanmamak için dikkatlı ol" ?
What is " ke" here?
I guess you're talking about 'ki' and I also guess it is 'that' here. :-)