Try doing a search, I believe there has been advice posted in this forum in the past regarding getting into derm and I know that there is advice in the old dermboard on yuku.
The short answer is derm is hard but not impossible to get into. There are many stellar derm applicants who have great board scores, mostly honors on 3rd year and away rotations, publications and/or research, and great LORs, so strive to get the same so that you are competitive. If you don't have any publications, or don't get great board scores, or don't honor every rotation then it is definitely still possible to get into derm but it is harder. I could be wrong but I believe that not getting honors in the first two years won't affect your application much at all, grades in the first two years are pretty low on the list of important factors given that many schools don't even give them out. Talking with your dermatology department chair or dean/advisor could help you gauge whether you should pursue derm.
As a 2nd year you really have no idea what most specialties are like. Even though you think you love skin and have a passion for it right now you may find during your clinical rotations that you also love delivering babies, or have a passion for surgery, and get bored seeing derm patients in clinic. For you, right now, your number 1 priority should be figuring out how to study so that you do your absolute best on step 1 (mean score amongst derm applicants who matched in 2007 was 238, http://www.nrmp.org/data/chartingoutcomes2007.pdf
), and then go into 3rd year rotations with an open mind and a determination to do well. You should also try to schedule a clinical or research elective in derm so that you start getting to know your department and find out whether you like the clinical/research side of dermatology, but if you focus on getting great board scores and doing well on clinical rotations then you will set yourself up well to match into whatever specialty you choose, derm or otherwise.