If you already set the min. price, you can't change that until the negotiation is over; it is already locked. But, you can manually accept any current low offer (less than 5 tokens). If you want 2 tokens, you can look for him on Facebook, and tell him to bid for 2T right now and you will accept, or to bid back again after the negotiation is over and after you have added him in your friend's list by clicking on the player in your team's squad page. You can negotiate for 2 tokens via Facebook messages; this won't be a big jump compared to his initial offer. If he does not accept, still 1 token is better than 0, especially if your team already has enough cash that you don't need the cash that will be provided by putting this player in the auction market.
It is the amount of tokens that go to Nordeus in negociations that makes it difficult for many managers. The increase in total tokens when you increase what goes to you is even more discouraging to potential buyers.