The striker, who had earlier been linked with a deadline day move to Leicester City, took his tally to 11 in time added on before the break.
A free-kick swung into Forest's box by new signing Jeff Smith was cleared only as far as Paul Thirlwell, on the edge of the area.
The midfielder lobbed the ball back over the advancing Forest defence and quick-thinking Hawley raced in to head past flat-footed keeper Paul Smith from six yards.
Carlisle had started brightly with Smith finger-tipping a header from Joe Garner over the bar in the sixth minute.
But Forest looked comfortable on the ball and in the tenth minute a Jack Lester pass sent ex-Carlisle favourite Scott Dobie through on goal, but he was driven wide and shot into the sidenetting.
Forest went a lot closer after 37 minutes when James Perch was left unmarked to meet a far-post cross from John Curtis, but he steered his header just wide from eight yards.
At the other end, Garner steered a header wide from a throw-in by Zigor Aranalde and then had a goalbound header cleared by central defender Ian Breckin, with keeper Smith in trouble.
After the break Forest went close to clawing back Carlisle's lead. A long throw into the box by Julian Bennett was allowed to reach Lester, whose snap-shot flew just over the angle of post and bar.
But Carlisle came close to doubling their lead in the 62nd minute when Wes Morgan failed to clear an awkwardly bouncing ball across the Forest box and Smith stole in, but his header landed on the roof of the net.
Forest made a double substitution in the 76th minute, with Junior Agogo and Nathan Tyson brought on up front.
But Carlisle finished the stronger, man of the match Paul Murray almost beating Smith with a sliding shot five minutes from time.