just noticed ive got a huge gash out of the sidewall on one of my front tyres

fook know how that happened, looks like its been kerbed or hit a pothole or something.
anyway, the tyre is a <2 month old T1-R (and it's on the front so isn't that worn)
now, i dont really fancy replacing BOTH front tyres, especially as theyre new...
can i get away with just replacing the fooked one and leaving the other side as it is? i know people do it all the time, but dunno if its actually wise or not.
like i said above, the tyres have only done about 1-2k and theyre not very worn (only just worn off the coloured lines!) so should i be ok?