The 24-year-old first took the knock during a Boxing Day clash with the Scarlets but admits the opportunity to face the world champions was too good to miss.
"I wanted to see how the final against Leinster went," said Hook - who was voted Welsh player of the year recently.
"I spoke to Warren after that and made myself available. It's the last game of the season and it's an opportunity for us to beat South Africa, so it was a no-brainer.
"I have gone through five or six months of the season now with the shoulder and I have made myself available for a great game.
"Obviously it's a problem that needs to be sorted, but an extra week shouldn't make any difference.
"I can't really do much more damage to it. It's just the pain factor and getting through that. It's a question of holding the pain basically.
"I am having pain-killing injections and that is helping me along.
"I am limited in terms of what I can do in training. For the last five months I have been managing it and doing what's best for myself really."