Especially for new guitar players, and depending on the type of guitar string you are using (steel vs nylon, for example), guitar playing can be quite stressful to the nails, resulting in chipping and cracking of the nail ends. However, the nails, like any other part of the body, due respond positively to stress, so most people find that with time the skin on the tips of the fingers thickens and the nails thicken as well. So, down the road, you might expect less of this nail damage from playing the guitar. Other strategies that you could employ would include switching to softer strings (nylon) if that fits the type of music you want to make, or using a guitar pick, which will help a lot with the stress you put on the nails by strumming. Also make sure that you keep the nails nicely trimmed and as short as possible, as longer nails are more likely to be stressed and fracture
from the playing. Nutritional deficiencies can cause splitting and cracking of the nails, especially iron or zinc deficiency. However, if you are otherwise healthy, it is much more likely that the splitting is just from playing and that you do not need to worry
about it more.