Is It Possible For HIV Infection Through Injuries?

Hello, i wish to know whether aid or Hiv or any std can be transmitted by holding the hand of an infected person. In fact i helped someone infected the other day to climb a small hump and on my hand there was a small injury. I fear that there might be any injury on the latter s hand as well. But fortunately after helping him , there was no blood on my hand but what i fear is that if there was an open sore (not bleeding) on his hand and while holding my hand ,his open sore come into contact with my injury. also note that the injury i had was quite recovered ,that is there was the temporary skin (mostly white & brown) which normally covers an injury.I mean when someone injure himself , he is sore will have a temporary skin during the recovery process then he or she will get back his normal skin, i mean the injury will disappear completely.... can hiv or any std be passed this way.Only by contact with an open sore (not bleeding)...