Strawberry Fruit Nubbins

There are several possibilities for the cause of the deformation of your strawberry fruit. In most cases these types of fruit deformations are called “nubbins”. We’ve included several links with pertinent info. We can’t be more specific because we don’t have all the information we need to ID the cause definitively, but you can compare what you know about growing conditions (including temperatures, fertilizers, insect presence, chemical applications, and etc) to the info in these links. You may be able to correct the growth of future fruits if its an issue that is caused by lack of fertilizer/nutrients, or if it was insect damage and the pests are now gone, maybe temps are evening out, and so on.
http://www.fruit.cornell.edu/berrytool/strawberry/flowersandfruit/strnubbiness.htm
http://strawberryplants.org/2010/05/growing-strawberries/
http://strawberryplants.org/2010/12/deformed-strawberries/