MySQL has a function WEEKthat you can use:
SELECT SUM(time)
FROM `time`
WHERE
`projectid` = '$pid'
AND created > NOW() - INTERVAL 2 WEEK
AND WEEK(created) IN (WEEK(NOW()), WEEK(NOW() - INTERVAL 1 WEEK))
Notes
(created > NOW() - INTERVAL 2 WEEK) , , , . , , . , .
"WEEK(NOW() - INTERVAL 1 WEEK)" - . WEEK(NOW()) - 1