Does weight matter?
 

For example if I weigh the same amount as my friend and we are the same height and she is chubby and a size 12 and I am a size 6 because I am made up of muscle. But we weigh the same so if i am thin but weigh more even though it's muscle does the number matter

Matter to who?
Body composition always matters in regards to health if that is what you mean.

Ask your Doctor or RD. None of us can know the answer to this question without seeing a blood/UA chemical profile and knowing the results of a compleate physical screening.

I second the question matter to whom? In this case I'd say no though. Weight is just a number, it's subjective. you can have 5 people that weigh, say, 130 with all 5 of them being at completely different levels of health.
Someone tall might be underweight, someone short may be overweight, someone 5'5 (falling right in the middle of normal by bmi chart) could have a high body fat %, a low body fat%, or a normal body fat % depending on their muscle tone (similar to you and your friends situation)

Ignore the number on the scale and worry more about how you feel about your body, how your clothes fit, etc

100 pounds difference matters- like the difference between 300lbs and 200. But does 20 pounds or even 30 pounds mean much? Not really. At those small numbers, it's really fitness that matters.

Weight is just a number which by itself is meaningless. This is why BMI by itself is meaningless because it is based on your height and weight only.