Do you have a tin that is a good tight fit around the pie? If so put it in the tin and let it cool/ set fully ( at least 8 hours) then make the gelatine stock and let that set until it is thickening. Pour it in and let it set , it should seal the crack and fill the pie. Alternately let the pie cool and set then turn it on its side , cracked side up and use the crack as the filling hole for the stock.You may have to stopper the 'normal' filling hole in the top somehow.
I make large pork pies and I have had this problem but got over itby one of the methods I have told you. One time I had to wrap the pie tightly in foil and cling film to seal a crack and fill it but it still worked.