Kabir, short version first so you can put the phone down: what you're describing, forehead swelling appearing on day 2 to 3, sliding to the eyes by day 4, worse on one side, is post-operative oedema, and it is one of the most predictable events in the whole recovery. It is not a sign that grafts are being crushed or starved. The swelling sits in the loose connective tissue of the forehead and eyelids, which is a long way, anatomically, from where your follicles were placed.
Where it comes from is worth knowing, because it takes the mystery out of it. During surgery a large volume of fluid, tumescent saline with a little adrenaline, is injected under the scalp to lift the skin and protect the vessels. Some of that fluid, plus the normal inflammatory response to hundreds of tiny incisions, has to go somewhere over the following days. Gravity carries it forward and down: off the rigid crown, across the mobile forehead, into the periorbital tissue around the eyes. That is why the top of your head, the actual graft site, usually looks fine while your face takes the hit. The one-sided asymmetry is the same principle, it follows whichever way your head rested overnight, exactly as norwood3ben found.
On timing, the pattern is fairly consistent: onset day 2 to 3, peak around day 3 to 5, largely resolved by day 6 to 7, and it does not scar or leave a mark. Sleeping at roughly 45 degrees for the first several nights genuinely reduces how far the fluid tracks forward, which is the real reason clinics push the upright-sleeping instruction, it is as much about swelling as about the grafts. On the frozen peas: LiamOD is right and I want to underline it, because it is the single most common well-meant mistake in this thread's territory. Cold and pressure never go on the recipient area in the first week; the grafts are anchoring and are mechanically vulnerable, which is the same reason the pillow threads exist. Any cooling belongs on the forehead below the hairline, and only if the team who operated on you signs off on it.
Now the part that matters more than any of the above: there is a version of facial swelling that is not this, and it is worth knowing the difference. Ordinary oedema is soft, painless, symmetrical-ish once it has settled, and cool to the touch. What warrants a same-day call is swelling that arrives with fever, that is hot, red and tender rather than just puffy, that is markedly and increasingly one-sided with pain, or that comes with discharge, because that picture can point to infection, which is uncommon (true post-transplant infection runs well under 1%) but is the thing worth ruling out. This general map of what is expected and what is not sits in the run-through of hair transplant risks and side effects. I cannot tell you which category your left eye falls into from here, and neither can anyone else in this thread, so if it turns hot or painful, that is a message to your clinic today, not a reply here. If it stays soft and painless and fades on the day-7 schedule, you have your answer already.
