I have a Hyundai accent and its normal tire size is 175/70 14″ . One tire has been punctured and I didn't noticed it so I drove it flat for about 16km and I just discovered it when I got home. I have another tire which is 175/65 14″. Is it okay to use it or should I replace it with the same size with the other 3.I cant use the old tire since its been severely damaged. So it would be 3 175/70 14" and one 175/65 14"
The difference in tire size will not be great, so driving it with a different size for the fourth tire shouldn't cause you any huge issues if used for short term. There is a concern here, though. You'll want to put the odd sized tire on the rear axle. This is for two reasons. One, on your Accent, the front end is the drive tires. Having them different sizes will cause extra wear on the differential. Secondly, it can also affect your braking ability, where one side can have more than the other. Since this is also your steering axle, having one side brake harder than the other can cause you steering issues. You will still get the braking differential in the rear of the car, but it won't cause the steering issues. Plus, since the rear only does about 30% of the braking, it won't be as noticeable there, either. I'm assuming your Accent does not have a tire pressure monitoring system (TPMS) or a dashlight would have indicated when the tire went flat in the first place. If this is a correct assumption on my part, you shouldn't have any issues with it being on, so you'll not have that issue to have corrected with the odd sized tire.
As I stated, you can use the tire most likely without any issues. You'll only want to use this as a temporary measure until you can get it replaced with the proper sized tire, though. It really isn't good for the car or for your safety to run differently sized tires.
I've been checking an online "Tire Size Calculator" for years to decide if different tires might be "close enough" to original equipment sizes.
The one at 1010Tires.com has been around a long time, and seems pretty good. It's at https://www.1010tires.com/Tools/Tire-Size-Calculator
It recommends "staying within 3% of the diameter of the original tire. Any more and you face the risk of brake failure."
Also, if your vehicle is an all wheel drive or 4WD you really do NOT want different sized tires on any different wheels, that can damage the AWD/4WD, follow the manual for those cases. (But having all 4 tires the same, just different from OEM sizes, could be fine).
Watch out for the new size tire or wheel being too big or having the wrong offset. Check for clearance to the fenders and brake/suspension parts. If you use tire chains/cables, consider that as well.
This is what 1010tires.com's calculator said about your tire sizes, the new one is the same width but a fair bit smaller (so should be ok for clearance) and just within the 3% recommended.
And Pᴀᴜʟsᴛᴇʀ2's answer is right about avoiding different size tires on the same axle, I wouldn't do any racing. You might want to consider it like driving with a compact spare tire and follow the owner's manual's recommendations (probably to stay under a certain speed like 80km/h or 50km/h, don't tow anything, etc).
Consider the cost of mounting & balancing the wrong tire, and then paying again to mount & balance the right tire later.