This looks like an injury that may have happened during mating. You may want to try separating her from any roosters, and any birds that may pack at it for a few days. Maybe try wrapping it in a small peice of gause.
In building my coop, the tips of some screws are exposed. Could this be a problem for the birds? If so (probably so) what can I put on the screws to make them less dangerous?
I'd be careful, you never know if they'll be half way done developing, and then your hen decides to stop being brudy. Also inconsistent temperature and humidity will not be good for the eggs.
If I were you, would go with a dorking because of their temperment. Dorkings will be very friendly, I once had a very nice dorking that could spend all day with you. Also, icelandics can be very hard to get.