At 25, a lump in the hand has nothing to do with the heart. The commonest causes are a ganglion cyst near the wrist or a lipoma - soft, mobile, painless and harmless. Sometimes it is a swollen tendon sheath from repeated gripping or phone/mouse use. What matters is whether it is soft or hard, fixed or mobile, and growing or stable.
Next Steps
Get a simple soft-tissue ultrasound of the swelling - it settles the diagnosis in minutes. Rush in if it becomes hard, fixed, rapidly growing, red-hot or starts affecting grip. Send me the scan on a Practo consult or show it at Synergy Miraj and I will tell you if it needs removal or just observation.