So far the only advice he's had is to get a solder sucker and start again, clearly there is more going on than that and he needs more experienced input, let's give him that instead shall we.

Flux cored or not something isn't right and it's probably a combination of things, additional Flux I think will help Ravi along in getting better joints, additional flux has been used in the SMD and rework/reflow arena's for years and for a very good reason!

What solder wire are you using?

Ravi, using additional flux cannot hinder the soldering process and can only assist you in doing a nice/better job, don't tell anyone this but that is the reason they put it in solder wire in the first place :).

Your soldering iron needs to be hot enough, balling up like that can come from the iron being too hot or cold, I'm betting yours is to cold, some lower end irons heat up but they don't do very well at staying hot once you start using them, this happens with low power irons too at around the 25w range, when you are trying to solder bigger components.

However my go to for most jobs is now a 12w Weller SP12, I inherited it along with technique from my grandfather who was a British telecom engineer, the iron is from around the 80-90's and still has the original tip, it along with a combination of technique, additional flux and a solder wire appropriately sized gets everything I solder just right for me - every time...Thanks Granddad!

40-60w is an average range on what allot of irons will be rated at, my other iron is a 25w similar to the Weller, I also have two gas soldering irons for mobile work. The bigger of the gas irons is handy with the tip removed as its basically a mini blow torch and works excellent on heat shrink and those jobs where you need a small flame with a bit more power.

What iron are you using ?

The tip of your iron needs to be "on point" Ravi, the problem comes from oxidation and not keeping your tip clean, once your tip becomes oxidized the solder will no longer want to flow or stick to it properly and this is a problem. Don't clean your tip in flux or water, this shocks the tip and damages the Iron and Chromium plating, just dip the tip in some pure Rosin after each joint and that should be good enough for the tips life time.

Solder to the tip of your iron and then to the area/joint to be soldered, your transferring the solder from one to the other, try and do this with as minimal amount of heat going into your component as you can and your now doing it correctly.

Soldering isn't rocket science Ravi, there are lots of options in terms of tools and technique but a few fundamentals need to be right for it to be successful, if left those balls of solder you've done so far could come lose and as such cause arcing, arcing not only damages components and equipment but it can cause fires too !!!!