@abhinavmail1 sorry you cannot use toothpaste or hair wax as thermal grease unless you want to burn the CPU. Neither of the substances is engineered to handle heat on its own...forget transfer it from the CPU heat spreader to the heat sink.
I can't believe you wiped off thermal paste @anant.del . But I think this shouldn't be the reason your PC isn't starting. Your computer will still be functional before it shuts off until it reaches the temperature of about 90°. This is the sign that the processor is overheating, it will shut down without any warning, but it will start. You can monitor the CPU temperature by SpeedFan application.
And until you're able to buy some thermal compound, you can use toothpaste.
It is hard to get Thermal paste during Lockdown. Toothpaste is not replacement of thermal paste as it dries out in few days. But it will work for few days. Anything better conductivity than air can work as thermal paste.
Toothpaste works very well but it dries up in a day or two and the temperature starts rising until CPU thermal throttles or shuts down . You'll have to open and replace it every couple of days but it does "work" if you really want to turn on the PC without it turning off in minutes.
Why not just leave the machine off? I really wouldn't advise anybody to risk the CPU unless of course it is considered dispensable. Heck, use a laptop, tablet or even your mobile phone till you get some thermal grease.
@abhinavmail1 once you take off a heatsink you automatically introduce an air bubble between the heat spreader and heat sink. Not ideal for heat transfer. Never take off the plain heat sink or a liquid cooler unless you have:
a) Isopropyl alcohol (or thermal paste cleaner) to clean the CPU and heat sink & remove ALL the old thermal paste and leave both surfaces spanking clean without even a dust spec on them.
b) Your choice of decent to good quality thermal paste.
I have been water/liquid cooling my home PCs since the early 2Ks and would not advise monkeying around with one of the most expensive parts of your PC build. Right now, both my home PCs run 240 mm Corsair AIO coolers because I can't be bothered with DIY kits as in the past there are too many overheads