7 days post wisdom tooth extraction & scab came off from lower. rinsed mouth with salt water and noticed a brown object in the sink. there is a hole on bottom. no severe pain. top has scab intact. i do have tmj. is this ok? is dry socket possible?

Yes can: The blood clot in extraction socket helps regenerate bone .If the lower right socket is empty & starts smelling and pain gradually increases ,you must see the Dentist who did extraction , he might have given you Antibiotic as prophylaxis otherwise if needed he will prescribe Antibiotic and pain medication as needed . TMJ problem at times increases after extraction due to wide opening of mouth .