Eating some lobster on a low carb diet is okay however just avoid eating too much lobster when on a low carb diet because it can be a bit high in carbs.
However lobster is not terribly high in carbs with around 6% carbs in each lobster but the lobster is also a bit high in calories which is around 114 calories in one small lobster.
The larger lobsters may contain around 230 calories so it can be fattening to eat too much lobster however it's not gonna hurt you or your diet to indulge on a little bit of lobster when on your low carb diet.
Just avoid eating too much lobster while your on your low carb diet.