I GOT A CENTIPEDE BITE ON MY THUMB WHICH I

I GOT A CENTIPEDE BITE ON MY THUMB WHICH I READ HAS VENEMOUS BITE 4 DAYS AGO WHILE I WAS WORKING IN THE SOIL AND IT GETS ITCHY, NUMB FOR A DAY AND NOW MY SKIN WHERE IT BIT ME HAS REDDISH COLOR. MY THUMB IS STILL A BIT SWOLLEN. WHAT CAN I PUT ON IT? I HAVE TRIED POLISPORIN, 1% WITH CORTOZONE AND STILL IT HASN'T HELPED. PLEASE TELL ME THE BEST WAY OF GETTING RID OF THIS PROBLEM.