Tie a line between the two bow dock cleats
. Use low streach line and make sure its tight. In the middle run another line, as thick as you have, from the dock
line onto the bow cleat of your boat. You could have two lines, one onto each bow cleat.
When you stand on the thick line the boat will come in a bit, reducing the gap and you can step off.
BTW if you stand on the line for too long you will get that sinking feeling, so adjust the stern lines appropriately.