Bet process when 2 players and Big blind is all in on the Pre-Flop
When the big blind goes all in that leaves the small bline with one chose if they would like to continue and see the hand and that is to call the bet by either going all in if they don't have enough to cover the bet or call it by betting the required amount. This is similar to if the big blind did a raise on the pre flop as the small blind would still need to match the difference.

In this case betting would end, both players would reveal their cards and the dealer would play the deck until all 5 cards have been played and a winner has been determined. There would be no side pot as in a two player game there is no other player to bet against so the only money that could be in the side pot would be the small blind's.